Morphological research on amniote eggs and embryos: An introduction and historical retrospective. (12th January 2021)

• Record Type: Journal Article
• Authors: Blackburn, Daniel G.; Stewart, James. R.
• Other Names: Matthias Starck J. guestEditor.; Blackburn Daniel G. guestEditor.; Stewart James R. guestEditor.
• Is Part Of: Journal of morphology. Volume 282:Number 7(2021)
• Page Start: 1024
• Page End: 1046
• Publication Date: 2021-01-12
• Subjects: amniote egg -- eggshell -- fetal membranes -- history of science -- placenta; Morphology -- Periodicals; Physiology -- Periodicals; Anatomy -- Periodicals; 571.3
• DOI: 10.1002/jmor.21320
• Languages: English
• ISSNs: 0362-2525

Abstract

Abstract: Evolution of the terrestrial egg of amniotes (reptiles, birds, and mammals) is often considered to be one of the most significant events in vertebrate history. Presence of an eggshell, fetal membranes, and a sizeable yolk allowed this egg to develop on land and hatch out well‐developed, terrestrial offspring. For centuries, morphologically‐based studies have provided valuable information about the eggs of amniotes and the embryos that develop from them. This review explores the history of such investigations, as a contribution to this special issue of Journal of Morphology, titled Developmental Morphology and Evolution of Amniote Eggs and Embryos . Anatomically‐based investigations are surveyed from the ancient Greeks through the Scientific Revolution, followed by the 19th and early 20th centuries, with a focus on major findings of historical figures who have contributed significantly to our knowledge. Recent research on various aspects of amniote eggs is summarized, including gastrulation, egg shape and eggshell morphology, eggs of Mesozoic dinosaurs, sauropsid yolk sacs, squamate placentation, embryogenesis, and the phylotypic phase of embryonic development. As documented in this review, studies on amniote eggs and embryos have relied heavily on morphological approaches in order to answer functional and evolutionary questions. Abstract : Amniotic (terrestrial) eggs of reptiles, birds, and mammals have been a major focus of morphological studies for centuries. This paper explores the history of such studies, and summarizes ongoing research on such aspects as gastrulation, egg and eggshell morphology, fetal membranes and placentation, embryogenesis, the phylotypic stage, and reproduction in extinct dinosaurs.